beneath the table to the abstract. Use the Word Count cmd under Utilites menu for counting Significance It is understood that the destruction of the auditory cortex results in a permanent deficit in the ability to determine the location of a sound in both humans and monkeys. However, it is not at all clear how individual neurons within the cerebral cortex could potentially contribute to this perception. Objectives Adult macaque monkeys are trained to perform a simple sound localization task wherein they are required to release a lever when the location of an auditory stimulus changes from one location to another. The activity of single cortical neurons are recorded while the monkey performs this task. The activity pattern of each neuron is then compared across all single neurons recorded from throughout several months of experiments to determine how all of these neurons fired during the presentation of each stimulus. Results Results to date are from approximately 400 single neurons. The population response of these neurons indicates that the activity is greatest when the sound is farthest from the same side of the head (contralateral), and gets weaker as the sound moves toward the same side of the head (ipsilateral) as the recorded neurons. This population code is consistent with behavioral data for localization of sounds both in azimuth (left-right) and elevation (up-down). Future Directions These experiments will continue until a full dataset are collected from each of three monkeys. Future experiments will entail determining how this population code is used by other parts of the cerebral cortex. KEY WORDS sound localization, primary auditory cortex, population response FUNDING NIH Grant DC02371 PUBLICATIONS Guard, D.C., Phan, M.L., Geiger, P.G., and Recazone, G.H. (1998) A population activity code of acoustic space in the primary auditory cortex (AI) of the macaque monkey. Soc. Neurosci. Abstr. 24:1402